Piezoelectric ceramic composition



Aug. 12, 1969V TsuNEo AKAsHl ET AL 3,451,071

PmzoELEcTRIc CERAMIC coMPosITIoN FIG. I

1N VENTORS MASA@ mmm sul fumo ramucu/ By Non/o rsusoucm rana/J aH/va rsu/vea Afmslw W g M Annemans.,

Aug 12, 1969 TsUNEo AKAsl-u ET AL 3,461,071

PIEZOELECTRIC CERAMIC COMPOSITION Filed Sept. 2, 1965 4 Sheets-Sheet 2 0.10 we/GHT 75 If 02 0.15 WEIGHT 7S' 6,2 03

Ppyan Haj )03W WEIGHTZMW flecmonfcMN/caz. coun/Iva Fna-ron 1N RAD/AL Move-(1b) I l (QM) Mec/umani. QUAL/ry mcrae 0 ,"g 1 1 f l l 0.00 0.0/ 0.02 0.03 0.05 0.10 020 030 0.50

FIGZ

INVENToRs.

MAsAo rAkAHAsH rau/a mmucm BY Namo rs1/500cm Aug. 12, 1969 Filed Sept. 2, 1965 LECTRoMec//AN/cnz. coun/N6 Maron IN maa/A1. Moos (if) TsuNEQ AKAsHl ETAL 3,461,071

PIEZOELECTRIC CERAMIC COMPOSITION 4 Sheets-Sheet 5 (am) scum/CAL Quaurr mcrae FIGB INVENTORS.

MAsAo mma/usm run/a rAuAucm von/o rsusoucwl BY roue. omva L 75l/NEO AKASHI ATQRNEKS.

AU8 12, 1969 TsuNr-:o AKAsHl ET L 3,461,071

Pmzomonm CERAMIC COMPOSITION Filed Sept. 2. 1965 4 Sheets-Sheet 4 ddd a0! a02 0.03 0.05 0.10 0.20 d 050 FIG. 4

I N VEN TOR 5 M4540 TAKAHSH/ UAI/0 YAMA ,r Non/o x rsu cH/ BY roue-J on 3,461,071 PIEZOELECTRIC CERAMIC COMIUSITION Tsuneo Akashi, Masao Takahashi, N orio Tsubouchi,

Tomeji Ghno, and Fumio Yamauchi, Tokyo, Japan, assignors to Nippon Electric Company Limited, Tokyo, Japan, a corporation of Japan Filed Sept. 2, 1965, Ser. No. 484,636 Claims priority, application Japan, Sept. 3, 1964, 39/5tl,522; Sept. 11, 1964, 39/51,971 Int. Cl. C04b 35/36 U.S. Cl. 252-623 3 Claims ABSTRACT F THE DISCLOSURE Piezoelectric ceramic of the general formula Pb (ZrxTiySnz) O3 where the subscripts denote mole fractions and have the following values: x=0.9, y=.1.6, z=0.65, and x+y+z=l.00, are improved by two coexistent additives; the first being .Ol to .50 weight percent manganese monoxide (MnO) and the second selected from the group of .0l to .30 weight percent iridium dioxide (IrOz) and .Ol to .50 weight percent chromium sesquioxide (Cr203).

This invention relates generally to piezoelectric ceramic materials, and in particular to novel lead titanate zirconate base ceramics characterized by the incorporation of manganese monoxide (MnO) and one of iridium dioxide (IrO2) and chromium sesquioxide (Cr203) as two c0- existent additive agents.

lt is the object of this invention to improve both the electromechanical coupling and the mechanical quality factors of piezoelectric ceramics.

It is well known that a solid solution of lead titanate zirconate [Pb(ZrTi)O3], produced by mixing together lead zirconate (PbZrO3) and lead titanate (PbTiO3) and sintering the mixture, exhibits enhanced piezoelectric properties, excellent temperature and time stability, and that the most salient piezoelectric properties are exhibited in the vicinity of x=0.52-0.54 for a generalized formula It is also known that the basic criteria for assessing the merits of piezoelectric ceramic materials are the electromechanical coupling factor kr and the mechanical quality factor Qm. The former indicates the conversion efficiency in converting mechanical oscillation to electrical oscillation and vice versa while the latter indicates the order of the energy consumed within the ceramic material in the oscillation conversion; the larger the value of the mechanical quality factor, `the less the amount o energy consumed.

Ceramic iilters using piezoelectric ceramics as elements and mechanical lters using the same as transducers have been the subject of considerable recent research. The characteristics of piezoelectric ceramics called for in these applications may be summed up as follows:

The electromechanical coupling factor of any ceramic filter element may maintain any designated value ranging from an extremely small value to an extremely large value and at the same time, the mechanical quality factor of the element must be as large as possible. When utilized as a transducer element, it is desirable that both the electromechanical coupling factor and the mechanical quality factor be as large as possible. In other words, the characteristics required for a transducer element conform to the characteristics of materials for ceramic filter elements having particularly large electromechanical coupling factors.

Although the principal constituent components con- United States Patent O Mice templated by this invention are lead titanate zirconate the effect of coexistence of manganese monoxide anc' iridium dioxide (chromium sesquioxide) as two additive: would remain the same even if 25 atom percent or les: lead in the lead titanate zirconate is replaced with any one or a combination of any two or all of calcium, stron tium, and barium; and/or 65 atom percent or less of tht sum of titanium and zirconium is replaced with tin. Thest are substitutions well Aknown to the art. Accordingly when hereinafter the term principal consituent compo nents is used or lead titanate zirconate is being describe: as a component, it will be appreciated that the descriptioi applies equally to one in which either or both of thx foregoing substitutions has been made. For further de tails of such substitutions, reference may be made to z treatise by B. Jaffe, R. S. Roth, and S. Marzullo' in tht Journal of Research of the National Bureau of Standards 55 (1955), page 239, and U.S. Patent No. 3,068,177.

It may be said therefore that this invention pertains t1 novel piezoelectric ceramic materials having essentiallj the constituency indicated by the generalized formula wherein the subscripts denote mole fractions and hav the following value:

and, if required or desired, 25 atom percent or less lea` is replaced with at least one of calcium, strontium, an barium; characterized by two co-existent additives as wi be described.

It will be further apparent to those skilled in the -ai that the improvements in the characteristics (kr and Qm caused by the incorporation of manganese monoxide an iridium dioxide (chromium sesquioxide) are due to mar ganese and iridium (chromium) ions present in lea titanate zirconate base ceramics. (Since iridium and chrc mium compounds are alternative second additive agent for convenience, the latter will be parenthetically recite to demonstrate that the use of either with -manganee compounds is intended.) Accordignly, manganese con pounds other than MnO (e.g., MnCO3 or Mn02) may l: employed; the only requisite being that such a compoun needs to contain the equivalent weight of manganes ions. Likewise, in incorporating an iridium compoun other than lrO2 (such as lrCl3 or Ir2O3) as a chromiur compound other than Cr203 (e.g., Cr2(SO4)3 or CrOS such compounds need to contain the equivalent Weigl of ions.

The above mentioned and other features and objec of this invention and the manner of `attaining them wi become more apparent and the invention itself will be be understood by reference to the following descriptic of embodiments of the invention taken in conjunctic with the accompanying drawings wherein:

FIG. 1 graphically illustrates the electromechanic` coupling and mechanical quality factors characterist of the piezoelectric ceramics of the invention with or additive constant.

FIG. 2 graphically illustrates the electromechanic coupling and mechanical quality factors characterist of the piezoelectric ceramics of the invention with tl other additive consatnt.

FIG. 3 graphically illustrates the electromechanic coupling and mechanical quality factors characterist of a piezoelectric ceramic with one variable additi alone.

FIG. 4 graphically illustrates the electromechanic coupling and mechanical quality factors characterist of a piezoelectric ceramic with the other variable additive alone.

The curves in FIG. 1 show the electromechanical coupling factor (abbreviated kr) in radial mode and the mechanical quality factor (abbreviated Qm) of piezoelectric ceramics having the principal constituent components expressed as Pb(Zr0.52Ti-48)03 and incorporating as the two additive agents 0.10 weight percent MnO, and: curve A-less than 0.30 weight percent Ir02 in varying amounts as the variable; and curve B-less than 0.50 Weight percent Cr203 as the variable.

It was experimentally verified that the values of kr and Qm for plain or unmodified lead titanate zirconate subjected to poling at room temperature were 41% and 270, respectively and that the corresponding values for the same ceramic subjected to poling at 100 C. were 42% and 250. FIG. 1 manifests that the incorporation of only 0.1 weight percent Mn0 contributes markedly to improvements in the piezoelectric characteristics and that incorporation of both M110 and Ir02 or Cr203 contributes to much greater improvements.

Incorporation of Ir02 in excess of 0.30 Weight percent impairs formation of a solid solution of lead titanate zirconate and Ir02, resulting in lowering of the electri- :al resistivity and impracticability of poling. Therefore, :he effective range for incorporation of Ir02 is restricted :o 0.30 or less ewight percent (0.00 wt. percent is exsluded). For similar reasons and reasons apparent from FIG. 1, the effective range of Cr203 is limited to 0.50 weight percent (0.00 wt. percent excluded).

FIG. 2 demonstrates the fact that the values of k,r 1nd Qm of a lead titanate zirconate ceramic containing only 0.10 weight percent 1,02 (0.15 weight percent Cr203) have been remarkably improved over the corresponding values of kr and Qrn of a plain lead titanate rirconate ceramic expressed as Pb(Zr052Ti0 48)03. It also demonstrates that more excellent piezoelectric prop- :rties can be secured under coexistence of Ir02 (Cr203) and MnO.

Further, improvements in the characteristics due to coexistence of the two additive agents cannot be expected vhere M110 exists in more than 0.50 Weight percent. Ihis is to say, the existence of the second addiitve Ir02 (Cr203) in the presence of more than 0.50 weight per- :ent MnO as the iirst additive does not materially im- Jrove the characteristics because the characteristics have )een fully aiiected by the iirst additive and stabilized. [n other Words, the coexistence of MnO and Ir02 ICr2O3) becomes of no further significance. For this eason the range of effective incorporation of MnO has neen restricted to 0.50 or less weight percent (0.00 weight Jercent is excluded).

The curves in FIG. 3 show dependence of kr and QIn )f piezoelectric ceramics consisting of a lead titanate zirconate expressed .as Pb(Zr0,52Ti0 48)03 and less than ).30 weight percent Ir02 (0.50 weight percent Cr203) in /arying amounts on the amount of Ir02 (Cr203) taken is the variable.

The curves in FIG. 4 show dependence of lcr and Qm )f piezoelectric ceramics consisting of a lead titanate zirconate expressed as Pb(Zr0 52T -48)03 and less than ).50 weight percent MnO in varying amounts on the imount of Mn0 taken as the variable.

The more detailed description which follows further :lariiies the invention and the relationship between the zmbodiments.

Lead oxide (PbO), zirconium oxide (Zr02) and ti- :aniurn oxide (Ti02) were mixed in the ratio of 50:26:24 nole percent so that theI principal constituent components nay be expressed as Pb(Zr052Ti0 48)03 and to this, re- ;uired amounts of manganese monoxide (MnO) and ridium dioxide (Ir02) were added. The mixture was :horoughly mixed in a ball mill, preheated at 900 C. for )ne hour, pulverized, and pressed to form disc-shaped 5amples. The samples were then sintered at 1300 C. for

.4 one hour and a pair of silver electrodes were installed on the opposite surfaces of each disc. Then the samples were subjected to poling either Iat room temperature or at C. by applying a voltage of 50 kv./cm. The samples Were then left standing in the air for twenty-four hours and the Values of icr and Qm of these ultimate products measured.

Normally, poling is performed at room temperature or at temperatures in excess of room temperature. In conducting these experiments, therefore, 100 C. was selected as a typical temperature above room temperature. Where the result was the same regardless of poling temperature, only one poling temperature will be described.

It is to be noted that (as will be seen from the tables) alternative ion sources were selected to illustrate the equivalency of additives (eg, in some cases MnC03 was used instead of MnO).

Table I shows the values of kr and Q11n for ceramics consisting of plain lead titanate zirconate, lead titanate zirconate and 0.10 weight percent MnO, and lead titanate zirconate, 0.10 weight percent Mn0, and less than 0.30 weight percent Ir02 in varying amounts, respectively.

TABLE I Poling kr No. Compositional formula temperature Percent Qm 1 Pb(Zl`o-52To-4g)03 ROODJ temp-.. 4l. 270 100 42 250 2 Pb(Zro.5aTo,is)O3 plus 0.10 Room temp 48 250 Wt. percent M110. 100 C- 55 260 3 Pb(Zr0,52Ti0,4g)0a plus 0.10 Room temp 50 500 Wt. percent MnO plus 100 64 470 0.01 wt. percent IrOz. 4 Pb(Zr0.szTi0,4s)O3 plus 0.10 Room temp 42 640 wt. percent MnO 1 plus 100 C 65 600 0.02 wt percent IrOz. 1 5 Pb(Zru.52Ti0 4g)O3 Plus 0.10 Room temp 43 360 wt. percent MnO plus 1100l 66 1, 140 0.05 Wt. percent Ir023. 6 Pb(Zrn.5zTIo rs)O3 plus 0.10 Room temp 67 1,060

wt. percent MnO 1plus 0.10 Wt. percent IrOz. 7 Pb(Zru.52Ti0 4a)O3 plus 0.10 Room temp 67 730 Wt. percent MnO plus 0.15 wt. percent IrOz. s Pb(Zro,s2Tiu,n) O3 plus 0.10 Room temp 62 630 Wt. percent 111x102 plus 0.20 wt. percent IrOz. 9 Pb(Xrn.s2Ti04g)O3 plus 0.10 Room temp..- 56 500 wt. percent MnO plus 0.30 Wt. percent IrOz.

1 0.10 Wt. percent MnO was incorporated.

s MnOg equivalent in amounts to 0.10 Wt. percent Mno was incorpora ted.

3 IrzOg equivalent in amounts to 0.05 wt. percent IrO was incorporated.

TABLE II Poling k, No. Compositional formula temperature Percent Qm 1 Pb (Zru-saTio-n) O3 Room temp 41 270 100 C 42 250 2' Pb(Zro s2Tio 4g)O3 plus 0.10 Room temp 48 250 Weight percent MnO. 100 0 55 260 3' Pb(Zra.52Ti0.n) O3 plus 0.10 Room temp.-- 44 460 Weight percent MnO plus 100 C 63 470 0.01 Weight percent Crzoa.

4 Pb(Z1u,5z Tinne) O3 plus 0.10 ROOm temp,... 41 560 Weight percent MnO1 plus 100 C 61 640 0.02 Wt. percent Crm.

5 Pb(Zro.szTin.4r) O3 plus 0.10 Room temp 37 820 Wt. percent M plus 0.05 100 0 62 1, 000 Wt. percent Crm.

6 Pb(Zru.s2Ti0 4s)O3 plus 0.10 Room temp.-- 45 1, 110 wt. percent MnO plus 100 59 1, 200 0.10 Wt. percent Crm.

7 Pb(Zrn nTu4g)O3 plus 0.10 Room temp 46 980 Wt. percent MnO2 plus 100 C 57 1, 010 0.15 Wt. percent Crm.

8 Pb(Zr0.5zTiu n)O3 plus 0.10 Room temp.-- 54 930 Wt. percent MnO plus 0.20 Wt. percent Crzoa.

9 Pb(Zr0.52Tio4.a)O3 plus 0.10 Room temp 46 780 wt. percent MnO plus 0.50 Wt. percent Crm.

1 Denotes incorporation of MnOZ in amounts equivalent to MnO. 2 Denoted incorporation n the form of MnO instead of M1102.

A comparison between samples No. 1 and No. 2 shows that incorporation of merely 0.10 weight percent MnO contributes appreciably to improvements in the value of kr. Further, a comparison between samples No. 3 through No. 9 and sample No. l or No. 2 demonstrates that both kr and Qm are improved markedly in the presence of both MnO and IrOZ as coexistent additives. These embodiments also indicate that these materials, notably No. 3 through No. 9, are eminently suitable for ceramic lter materials for which large values of kr are necessary or for transducer materials. It can further be noted that in the products consisting of lead titanate zirconate expressed as Pb(Zr0 52Ti0,48)O3 0.20 wt. percent IrOz, and varying amounts of M110..

A comparison between samples No. 1 land No. 17 shows that the incorporation of 0.20 weight percent IrO2 alone range where the inco oration of IIO2 is small (such as is effective for an im rovement in kr. Further, a com ari- P samples No. 3 through No. 5) the value of kr 1s markedly son between samples No. 18 through No. 21 and sample improved by poling at 100 C. No. 1 or No. 17 shows both Icr and Qm can be markedly Table II illustrates similar results are attainable with improved by incorporation of MnO and IrO2 as c0- Cr203 rather than Ir02 as the second additive. From this lo existent additives.

e l l table it may be seen that samples No. 3 through No. 7 TABLE V subiected to poling at 100 C. would be excellent for P un k o g ceramic filter elements for which particularly large values No. compositional formula temperature Percen Qn of k1. are called or vfor transducer elements in mechanical 17 13b@ T. )o 1 020 R t 59 35| r T r0.5n 10.45 :pus 00m empilters and that samples No. 3 through l\0. 9 subjected to 15 M mmm 1,02 100@ 58 40, poling at room temperature could be adapted for ceramic 18 maitenant?. plus 0.01 Rogm tempei 451 filter elements for which extremely large values of Qm mj rrg plus 0'20 100 C 57 46' and values of k of this order are necessa 19 Pb(Zru.5zT10.ii)Oi plus 0.05 Room temo-- 60 73* r ry Wt ce tM O 1 s Table III shows the experimental result obtained with O Zlplmet Irpo; Pb (Zr0 52Tin,48)O3, 0.10 weight percent IrO2, and less 20 20 Pb(' Zr0.5iTio.i)\/CI 38111S10.20 Room temp- 62 56 W .percen 1 n pus than 0.50 weight percent MnO in varying amounts. 21 Pgzzo wt'pert Ifoz 30 R t 60 43 r052 10.48 BpllS 00m 6mp--. l TABLE III vpecent MrC ruZs W.percen r z. Paling k, N0. 00111130511511311111 OI'm-la temperatur@ Percent Qm 25 MlInOg was incorporated in amounts equivalent to 0.20 Wt. percen Pb(Zro.a2Ti0.1s)O2 plus 0-10 ROgm 13911113- 52 320 2Ir03 was incorporated in amounts equivalent to 0.20 Wt. percen perrclent 1502.1 o 0l 1100 C t 62 210 OL 11 P r0.52 10.45 sDlS 00m emp... 57 00 Wt. percent MnO plus 63 410 9 Henzo wtpercanr IIrOz 02 R t 59 560 Table VI shows the experimental results with ceramii L rr(t.ri0 `t5i2rcits)i/1il,s1us logglfn: 62 520 30 products consisting of lead titaiiate zirconaate expresse( 0.10 Wt. percent IrOzas Pb Zr Ti O 0.20 wei h ercent MnO an( is Pbttzrtsi'riaahiu 0.0)51U noomtemp.-- 03 700 Crzoa i(n vlinglloms g t p W.p8I`Cel1l11 pus n 14 Pgvg- D'iq'clrso 20 Room temp 61 930 A remarkable increase 1n the value of both kr and QI 0.52 0.48 3 I l i M percent no plus for samples Nos. 18 and 19 subjected to poling at 100 0.10 Wtprcent Ir02- ov sa f 1 b'ect t oli 100 Pbtzm'SZTOBiJaluO'BO Room temp" 61 640 35 reailrillheevidrgitlfgorn7thsis1 elzmbmddircriit Ilguther iti X .percen l'D. 3131.15 7 010Wt-pr0ent1r0z noted that although any one of the values of k for sam Z 1 o.' f 16 Priv t-rio2rr`iiisiwiri su 5111;() Roomtemp 54 490 ples Nos. 20 through 22 sub1ected to poling at roor 010Wtper11t1`02 temperature is less than the value of kr for the sampl 10m Wepercent M110 Wasincorpomte@ 40 No. 17' containing MnO alone, any one of the corre 2 B CIInCC),2 was incorporated equivalent in amounts to 0.30 wt. percent Sponding values of Qm for the former Shows a marke. 36.53 W't erCentMnO mm @ratei increase over the value of m for the latter.

p p 4 lr03 incorporated in amounts equivalent to 0.10 Wt. percent IrOz.

TABLE Iv TABLE VI Poling k.- Poling kr No. Compostioual formula temperature Percent Qm No. Compositional formula temperature Percent Q 10 Pb(Zrn.52Ti0 45)O3 plus 0.15 Room temp." 47 750 17 Pb(Zru.szTi0.4s)O3 plus 0.20 Room temp 60 32 wt. percent CrzOi. C. 50 760 Wt. percent MnO. 100 C 64 31 11' Pb(Zr0.5gTi0,4i)O3 plus 0.01 Room temp. 52 780 18 Pb(Zru.52Ti.4g) O3 plus 0.20 Room temp.-- 35 5: wt.5perceut MrOCplis 100 C 53 850 Wtperceut MntO plts 100 C 67 5I 0.1 w .percen r2 3. 0.0 wt.percen Cri 12' Pbtzr0-5i'1i01oo3p1us 0.02 Room temp--- 54 820 50 19' Pb(zr.'1i...)o3p1us 03.20 Room renin-- 31 5: wtpercent MnOCplis 100 C 55 860 wt. percent MrO plis 100 67 5` 0.1 percen r2 3. 0.02 wt. percen Cri 3. 13 Pb(Zr0 5;Ti04g)O3 plus 0.05 Room temp 53 950 20 Pb(Zr.5gTiu.4g)O3 plus 0.20 Room temp 44 1, 2f petrLcent MntOCl pus 100 C- 55 950 Wt. percent MnOC1 plus 100 C 58 1, 2t 5w .percen rz a. 0.10 Wt. percent m03. 14 Pb(Zro.52Tio ii)O3 plus p.15 Room temp..- 45 1,080 21' Pb(Zr0.52Tiu.ii)O3 plus 0.20 Room temp. 58 1,14

Wt. percent boing plus 0.15 100 C 61 1, 170 5 5 wt. percent MnO plls w percen r2 i. 0.20 wt percent Cri 3. 15 Pb(Zr0 5zTi0.ii)O3 plus p.20 Room temp." 46 1, 060 22' Pb(Zr0.52Tiu.4g)03 plus 0.20 Room temp 45 1, 0:

Bvpertcent Mnglu 100 C 57 1, 150 wt. percent MnO plis w .percen r2 a. 0.30 Wt. ercent Cr is' PbtZrmTioiooa pius 0.50 R00mtemp 45 010 p 2 3 wt. percent M plus 1 M1102 was incorporated in amounts equivalent to MnO. 0.15 wt. percent 01u03. 60 1Denotes equivalent amount of MnOz was incorporated in lieu of MnO. Table VII ShOWS 'the eXperimeIlal results With peZ( electric ceramics consisting of lead titanate zirconat ,A Comparfson between Samples NO- 1 md NO- 10 Pb (Zr0,52Ti0.48)O3 as the principal constituent comp( eVmCS the mcorpof'tlon of OIY 0-10 Welgt Percent nents, 0.15 weight percent MnO, and 0.00, 0.05, and 0. IrOz is alreadyeffective for an improvement 1n kr. Fur- 65 Weight percent (3l-203 as the coexistent additives. ther, a comparison between samples No. 1l through No. 16 and No. l or No. 2 demonstrates `that both kr and Qm TABLE VII are markedly improved by the coexistence of MnO and Poling k IOZ Ilt Cal further be1 n0ted thato by :Omparmg samples No. Compositional formula temperature Percent C No' l an No' 121.130 mg at 100 C 1S consldeably ad` 70 23' Pb(Zr.5iT10.1i Oa plus 0.15 Room temp--- e9 i vantageous over po ing at room temperature for improvel Wt, percent Mno. 100 c 0s a ment of kr, but the value of Qm is substantially unaiected 24 Pllvuzfg'gl ROOll tempuby the diierence in the poling temperature. 25' Pgzoz' wt'perelt (12mg. 5 R -t 48 1.1

n.52 10.48 3p us .1 oom emp... Table IV shows similar results with Cr203 1n lieu of Wt'percem MBO plus 1000 67 1,1

Table V shows the experimental results with ceramic 0.10 wt. percent CriOs.

The value of kT for any one of samples No. 24 and No. subjected to poling at 100 C. becomes a little less than that for corresponding sample 23 containing MnO alone, Whereas the value of Qm for the former has increased rnarkedly over that for the latter. It may be said therefore that these materials, notably No. 24 and No. 25, are adapted for ceramic filter elements for which particularly large values of kr are called or for transducer elements in mechanical iilters.

It can be further noted that the value of kjr for either of samples No. 24 and No. 25 subjected to poling at room temperature has been decreased markedly from that for corresponding sample No. 23', Whereas the value of Qm for the former has been markedly increased. It may be said therefore that these materials, notably No. 24 and No. 25 (subjected to poling at room temperature) are adapted for ceramic lilter elements for which values of kr of this order are required.

The values of lcr and QIn for a ceramic material consisting of lead titanate Zirconate expressed as 0.01 Weight percent MnO, and 0.30 Weight percent IIOZ (sample No. 22) and subjected in poling at room temperature were 60% and 460, respectively.

The values of kr and Qm for a ceramic material consisting of the same principal constituent compositions as sample 22 and 0.30 weight percent Ir02 (let this be called sample No. 23) were 52% and 325, respectively.

A comparison between these samples readily reveals that the incorporation of traces of MnO (e.g., 0.01 wt. percent) is elective for an improvement of both kr and Qm. The corresponding values of kr and Qm for the same ceramic materials subject to poling at 100 C. remained substantially unchanged.

Table VIII shows the experimental results with piezoelectric ceramics consisting of PbO, ZrO2, TiO2 so that the generalized formula is:

(for which x=0.50, 0.53, and 0.55) incorporating as coexistent additives 0.10 weight percent MnO and 0.10 weight percent 1r02. All of these samples were subjected to poling at room temperature.

TABLE VIII No. Compositional formula percent Qm 24 Pb(Zf0.45TO.55)O3 8 320 25 Pb(Zr0.45Ti0.55)O3plus0.10wt.percentMnO 28 1,650

plus 0.10 Wt. percent IrOz. 2G Pb(Z!`0.50TO.50)O3- 27 350 27 Pb(Zru.suTio.so)O3 plus 0.10 wt. percent MnO 47 1,230

plus 0.10 wt. percent IrgOz. 28 Pb(ZI`0.53TO.47) O3 41 300 29- Pb(Zrt.saTio.41)Oa plus 0.10 wt percent 62 970 MnO1 plus 0.10 Wt. percent 11'02. 30 Pb(ZI`U.55TO.45) O3. 38 320 31 Pb(Zr0.55Tio.45)O.-. plus 0.10 Wt. percent MnO plus 0.10 Wt. percent IrOg. 51 1,470

llnOz incorporated in amounts equivalent to 0.10 Weight percent It can be noted that the values of kI and Qm for ceramic materials containing 0.10 weight percent MnO and 0.10 weight percent IrOz have been improved markedly over those for plain lead titanate zirconate in spite of the changes in the compositional ratio of Zr to Ti shown.

We claim:

1. A piezoelectric ceramic of the general formula wherein the subscripts denote mole fractions and have the following values: x=0-.9, y=.1-.6, z=0.6\5, and x+y+z=l.00, said ceramic having incorporated therein a iirst additive of from .01 to .50 weight percent manganese monoxide and a second additive of 0.1 to .30 weight percent iridium dioxide, said iirst and second additives being coexistent in the ceramic.

2. The ceramic claimed in claim 1 with 0-25 atom percent lead replaced with one or more bivalent elements selected from the group consisting of calcium, strontium and barium.

3. The ceramic claimed in claim 1, wherein one or more of said manganese monoxide and iridium dioxide are replaced with, respectively, a magnesium compound other than manganese monoxide and an iridium compound other than iridium dioxide having the equivalent ion Weight.

References Cited UNITED STATES PATENTS 3,006,857 10/ 1961 Kulcsar 252-629 3,268,453 8/1966 Ouchi et al. 252-62.9

3,347,795 10/ 1967 Akashi et al. 252-62.9

TOBIAS E. LEVOW, Primary Examiner R. D. EDMONDS, Assistant Examiner U.S. Cl. X.R. 

